Variable light distribution type headlamp

Abstract

A variable light distribution type headlamp which provides an optimum irradiated beam pattern under all driving conditions. The headlamp includes a projector lamp, a fixed lens, and a movable lens disposed on the optical axis of said projector lamp forward of said projector lamp. The movable lens is a condensing lens, and the fixed lens being a cylindrical concave lens. The focal length and a range of movement of the movable lens are such that front focal points of the movable and fixed lenses coincide when both lenses are close to each other. A lens drive mechanism controls the position of the movable lens in both X and Y directions so as to respectively control the amount of beam diffusion and beam direction in accordance with the vehicle speed and steering direction.

What is claimed is: 
     
       1. A variable light distribution type headlamp comprising: a projector lamp, a fixed lens, and a movable lens disposed on the optical axis of said projector lamp forward of said projector lamp, said movable lens being a condensing lens, said fixed lens being a cylindrical concave lens, a focal length and a range of movement of said movable lens being such that front focal points of said movable and fixed lenses coincide when both lenses are close to each other. 
     
     
       2. The variable light distribution type headlamp as claimed in claim 1, wherein said movable lens is a Fresnel lens. 
     
     
       3. The variable light distribution type headlamp as claimed in claim 2, wherein a shape of said movable lens toward lens steps thereof is aspherical. 
     
     
       4. A variable light distribution type headlamp comprising: a projector lamp; a fixed lens and a movable lens disposed on an optical axis of said projector lamp forward of said projector lamp, the light distribution pattern of an irradiated light beam produced by said lamp being controlled by moving said movable lens so as to vary the distance between said fixed and movable lenses, and the direction of said irradiated beam being controlled by moving said movable lens perpendicular to said optical axis of said projector lamp; a lens mount, said movable lens being fixed to said lens mount; a lens carrier, said lens carrier being slidably mounted to slide in a direction of an X-axis extending parallel to said optical axis; a Y-axis screw shaft, said Y-axis screw shaft being rotatably supported by said lens carrier and extending in a direction perpendicular to said X-axis, one end of said lens mount being threadedly engaged with said Y-axis screw shaft; an 17 X-axis screw shaft extending parallel to said optical axis, said lens carrier being threadedly engaged with said X-axis screw shaft; an X-axis drive motor; a Y-axis drive motor; a first rotary transmission mechanism for rotationally coupling said X-axis drive shaft to said X-axis motor; a tubular shaft extending parallel to said optical axis; a slide shaft, one end of said slide shaft slidably extending into said tubular shaft, said slide shaft rotating together with said tubular shaft; a second rotary transmission mechanism for rotationally coupling said slide shaft to said Y-axis drive shaft; and a third rotary transmission mechanism for rotationally coupling said tubular shaft to said Y-axis drive motor, wherein the light distribution pattern of said irradiated beam is variably controlled by operating said X-axis drive motor to move said movable lens so as to vary the distance between said movable and fixed lenses, and the direction of said beam is variably controlled by moving said movable lens perpendicular to said optical axis of said projector lamp by operating said Y-axis motor. 
     
     
       5. The variable light distribution type headlamp as claimed in claim 4, wherein said movable lens is a condensing lens, and said fixed lens is a cylindrical concave lens. 
     
     
       6. The variable light distribution type headlamp as claimed in claim 5, wherein a focal length and a range of movement of said movable lens are such that front focal points of said movable and fixed lenses coincide when said movable and fixed lenses are close to each other. 
     
     
       7. The variable light distribution type headlamp as claimed in claim 6, wherein said movable lens is a Fresnel lens. 
     
     
       8. The variable light distribution type headlamp as claimed in claim 7, wherein a shape of said movable lens toward lens steps thereof is aspherical. 
     
     
       9. The variable light distribution type headlamp as claimed in claim 4, wherein said slide shaft has a pin fixed thereto slidably received in a slot formed in said tubular shaft, whereby said slide shaft can slide with respect to said tubular shaft but rotates together with said tubular shaft. 
     
     
       10. The variable light distribution type headlamp as claimed in claim 4, further comprising a pair of pivot shafts for tiltably mounting said projector lamp. 
     
     
       11. The variable light distribution type headlamp as claimed in claim 4, wherein a forward end of said slide shaft is rotatably supported on said lens carrier. 
     
     
       12. The variable light distribution type headlamp as claimed in claim 4, further comprising: a bearing holder, one end of said lens carrier being secured to said bearing holder; a Y-axis guide extending parallel to said optical axis, said bearing holder being slidably fitted to said Y-axis guide.